If you've ever tried to compile ffdshow tryouts and received this error -

yasm: warning: can open only one input file, only the last file will be processed
yasm: FATAL: Could not open input file

The problem is spaces in the project path (i.e. D:\Documents\Visual Studio 2008\Projects\ffdshow-tryout\trunk) that aren't properly enclosed in quotes.  Easiest thing is to move the folder, but hopefully the project admins will accept a patch and save everyone the trouble.